Effects of Management Practices on Grassland Birds:

Marbled Godwit

This report is one in a series of literature syntheses on North American grassland birds. The need for these
reports was identified by the Prairie Pothole Joint Venture (PPJV), a part of the North American Waterfowl
Management Plan. The PPJV adopted the goal to stabilize or increase populations of declining
grassland- and wetland-associated wildlife species in the Prairie Pothole Region. To further that objective,
it is essential to understand the habitat needs of birds other than waterfowl, and how management practices
affect their habitats. The focus of these reports is on management of breeding habitat, particularly in the
northern Great Plains.

Organization and Features of this Species Account

Information on the habitat requirements and effects of habitat management on grassland birds were
summarized from information in more than 5,500 published and unpublished papers. A range map is
provided to indicate the relative densities of the species in North America, based on Breeding
Bird Survey (BBS) data. Although birds frequently are observed outside the breeding range
indicated, the maps are intended to show areas where managers might concentrate their attention.
It may be ineffectual to manage habitat at a site for a species that rarely occurs in an area.
The species account begins with a brief capsule statement, which provides the fundamental components
or keys to management for the species. A section on breeding range outlines the current breeding
distribution of the species in North America, including areas that could not be mapped using BBS data.
The suitable habitat section describes the breeding habitat and occasionally microhabitat
characteristics of the species, especially those habitats that occur in the Great Plains.
Details on habitat and microhabitat requirements often provide clues to how a species will
respond to a particular management practice. A table near the end of the account complements
the section on suitable habitat, and lists the specific habitat characteristics for the species
by individual studies. A special section on prey habitat is included for those predatory
species that have more specific prey requirements. The area requirements section provides
details on territory and home range sizes, minimum area requirements, and the effects of patch
size, edges, and other landscape and habitat features on abundance and productivity. It may be
futile to manage a small block of suitable habitat for a species that has minimum area requirements
that are larger than the area being managed. The Brown-headed Cowbird (Molothrus ater) is an
obligate brood parasite of many grassland birds. The section on cowbird brood parasitism summarizes
rates of cowbird parasitism, host responses to parasitism, and factors that influence parasitism,
such as nest concealment and host density. The impact of management depends, in part, upon a species'
nesting phenology and biology. The section on breeding-season phenology and site fidelity includes
details on spring arrival and fall departure for migratory populations in the Great Plains, peak
breeding periods, the tendency to renest after nest failure or success, and the propensity to
return to a previous breeding site. The duration and timing of breeding varies among regions and
years. Species' response to management summarizes the current knowledge and major findings in the
literature on the effects of different management practices on the species. The section on management
recommendations complements the previous section and summarizes specific recommendations for habitat
management provided in the literature. If management recommendations differ in different portions of
the species' breeding range, recommendations are given separately by region. The literature cited
contains references to published and unpublished literature on the management effects and habitat
requirements of the species. This section is not meant to be a complete bibliography; for a searchable, annotated bibliography of published and unpublished papers dealing with habitat needs of grassland birds and their responses to habitat management, use the Grassland and Wetland Birds Bibliography on the home page of this resource.

Figure. Breeding distribution of the Marbled Godwit in the United States and southern Canada,
based on Breeding Bird Survey data, 1985-1991. Scale represents average number of individuals detected per
route per year. Map from Price, J., S. Droege, and A. Price. 1995. The Summer Atlas of North American Birds,
Academic Press, London, England. 364 pages.

Keys to management include providing large expanses of short, sparse to moderately vegetated
landscapes that include native grasslands and wetland complexes. Wetland complexes contain a diversity of
wetland classes and sizes, such as ephemeral, temporary, seasonal, semipermanent, and permanent wetlands,
as well as intermittent streams. Marbled Godwits use wetlands of various salinities.

Breeding Range:

Marbled Godwits breed from central Alberta through central Manitoba and along St.
James Bay, south through Montana, North Dakota, eastcentral South Dakota, and northcentral
Nebraska, and east to northcentral Minnesota (National Geographic Society 1987).
(See figure for the relative densities of Marbled Godwits in the United States and southern
Canada, based on Breeding Bird Survey data.)

Within wetland habitats, Marbled Godwits avoided dense emergent vegetation, preferring shallow water
areas with short, sparse to moderately dense shoreline vegetation (Ryan 1982, Ryan et al. 1984, Eldridge 1992).
Suitable wetlands ranged in salinity from fresh to highly saline, and varied widely in size and permanence
(Stewart and Kantrud 1965, Stewart 1975, Ryan et al. 1984, Eldridge 1992, Prescott et al. 1995). Semipermanent wetlands were used
most often, but ephemeral, alkali, and temporary ponds were preferred relative to their availability
(Ryan et al. 1984). Kantrud and Stewart (1984) observed 57% of breeding Marbled Godwits using seasonal
wetlands, but their density was highest on temporary wetlands. Shifts in wetland use occurred seasonally
and during climatic extremes, as breeding Marbled Godwits used less-permanent wetlands early in the breeding
season and moved to semipermanent and alkali wetlands later in summer or during drought (Ryan et al. 1984,
Gratto-Trevor 2000). In North Dakota, Marbled Godwits nested in wet and dry areas of wet meadow,
upland areas of short (<30 cm) grass, and idle mixed-grass hayland; they fed in dry uplands, wet and dry areas
of wet meadow, roadside ditches, and open water (Nowicki 1973). In southern Alberta, average distance
between nest sites and water was 239 m in managed wetlands and 258 m in natural wetlands
(Gratto-Trevor 2000). In Saskatchewan, Marbled Godwits nested in wetland margins and uplands with
denser, taller, and more homogeneous vegetation than random sites (Colwell and Oring 1990). A table near
the end of the account lists the specific habitat characteristics for Marbled Godwits by study.

Area requirements:

Territories are large, and include both feeding and nesting areas. Areas must be large enough to provide both
upland habitat and a diverse range of wetland types (Ryan et al. 1984, Colwell and Oring 1988a, Kantrud
and Stewart 1984). In North Dakota, mean territory size was 90 ha (Ryan et al. 1984). Marbled Godwits may
be area sensitive, rarely occurring on blocks of contiguous grassland <100 ha in the northern
Great Plains (D. H. Johnson, unpublished data).

Brown-headed Cowbird brood parasitism:

No known records of brood parasitism by Brown-headed Cowbirds (Molothrus ater) exist.

Breeding-season phenology and site fidelity:

The breeding season extends from mid-April through late July (Maher 1973, Stewart 1975, Kantrud and
Higgins 1992, Sedivec 1994, Gratto-Trevor 2000). The earliest reported nest with eggs was
17 April (Stewart 1975), with most nests initiated during mid- to late May (Maher 1973, Kantrud and Higgins
1992, Sedivec 1994). Kantrud and Higgins (1992) report a late hatching date of 27 June, and
Stewart (1975) observed a dependent brood 18 July. One brood is produced per season (Gratto-Trevor 2000).
Although Higgins et al. (1979) reported that Marbled Godwit pairs appeared to make only one nesting
attempt per breeding season, Ryan et al. (1981) and Gratto-Trevor (2000) reported that renesting
occurred after failure of the initial nest. Marbled Godwits begin flocking in mid- to late July
(Maher 1973), and most flocks depart by late August (Ryan et al. 1984). In Saskatchewan and Alberta,
Marbled Godwits exhibited breeding-site fidelity (Colwell and Oring 1988b, Gratto-Trevor 2000).

Species' response to management:

Marbled Godwit densities were highest during the first 2 yr after a burn in North Dakota grasslands
(Johnson 1997). Ryan et al. (1984) suggested that fall burning or haying could provide nesting habitat the
following spring, and the denser, taller regrowth (15-60 cm) could provide suitable habitat for broods.
Haylands are readily used by breeding Marbled Godwits (Ryan et al. 1984, Kantrud and Higgins 1992).

Grazing can be used in both upland and wetland habitats to maintain the short, moderately dense vegetation
preferred by Marbled Godwits (Ryan et al. 1984). Grazed or recently grazed uplands are often more
attractive to breeding Marbled Godwits than are other land-use types (Ryan et al. 1984, Renken and
Dinsmore 1987, Kantrud and Higgins 1992, Sedivec 1994). In Saskatchewan, no significant difference in
abundance was found between lightly grazed mixed-grass and lightly grazed stands of crested
wheatgrass (Agropyron cristatum) (Sutter and Brigham 1998). In North Dakota, density of Marbled
Godwits was not significantly different among several rotational grazing systems and idle pastures
(Messmer 1990). The rotational systems were season-long pasture, short-duration (involves a system of
pastures rotated through a grazing schedule of about 1 wk grazed and 1 mo ungrazed, repeated
throughout the season), and twice-over rotation (involves grazing a number of pastures twice per season,
with about a 2-mo rest between grazing).

Management Recommendations:

Maintain a diverse complex of wetlands (Kantrud and Stewart 1984, Ryan et al. 1984, Colwell and
Oring 1988a). Marbled Godwits used wetlands of widely varying types and salinities, and may need
to utilize larger, more-permanent wetlands during droughts or late in summer (Ryan et al. 1984). Maintain
shallow-water ponds with little or no emergent vegetation for pre- and post-breeding flocks and shallow-water
ponds with margins of emergent vegetation for broods (Gratto-Trevor 2000).

Fall burning or mowing of upland sites and wetland edges can produce suitable cover
for the following spring (Ryan et al. 1984). Moderate to dense regrowth in burned
areas may be too dense for nesting, but can provide the denser, taller cover used
by broods (Ryan et al. 1984).

Marbled Godwits prefer previously grazed areas that are idle during the current breeding season
(Kantrud and Higgins 1992). If grazing is used, choose rotational grazing over season-long grazing
(Sedivec 1994). When implementing a rotational grazing system, avoid grazing until late May or late
June (Sedivec 1994, Gratto-Trevor 2000); when using season-long grazing, delay grazing until mid-June
(Sedivec 1994). Berkey et al. (1993) suggested that short-term grazing (2-4 wk in May) may be beneficial to
Marbled Godwits in North Dakota.

Nested in native grassland, were most common in pastures idle during current growing season;
nest sites were characterized by short to intermediate vegetation height and density; used areas with
<40% dead vegetation; avoided areas with 100% visual obstruction >10 cm and areas with >35 cm effective
cover height (average maximum height of leaf canopy); average effective cover height at nests was 17 cm

No significant difference in density between grazing treatments, although short-duration (system of
pastures rotated through a grazing schedule of about 1 wk) and twice-over deferred (pastures grazed
twice per season with 2-mo rest between grazing) grazing systems had higher densities than season-long grazing
system (leaving cattle on the same pasture all season); nested on silty, thin upland, and shallow-to-gravel
range sites

Nested in wet and dry areas of wet meadow, upland areas of short (<30 cm) grasses, and idle mixed-grass hayland;
foraged in dry grasslands, wet and dry areas of wet meadows, in roadside ditches, and in open water

In wetlands, were most abundant in large saline wetlands and were also found in large fresh,
small saline, and medium fresh wetlands; in uplands, were most abundant in idle native grassland and
continuously grazed native grassland

Preferred uplands with short (<15 cm for nesting pairs, 15-60 cm for pairs with broods),
sparse to moderately dense native grasses; avoided tilled land; used pasture, grassland and hayfield
habitats; used a variety of wetland types characterized by short, sparse to moderately dense shoreline
vegetation; used semipermanent ponds most frequently but select ephemeral, alkali and temporary ponds if
available; used alkali and semipermanent wetlands more often in dry years; mean territory size was 90 ha;
territories contained more wetlands and wetland classes than randomly selected areas

Sedivec 1994

North Dakota

Idle mixed-grass, mixed-grass pasture

Nested in dry upland; were more common in grazed areas than ungrazed areas; nested in sparse
vegetation with low height density (<6 cm); native rangeland should not be grazed until late-May to
early June when implementing rotational grazing, and season-long grazing should be delayed until mid-June

Nested in native prairie, cropland, and hayland; used a variety of wetland types that varied in
salinity from fresh to highly saline

Stewart and Kantrud 1965

North Dakota

Wetland

Highest densities were found on seasonal wetlands with closed stands of emergent cover or with
clumps of emergent cover interspersed with open water; on semipermanent wetlands with closed
stands of emergent cover, with clumps of emergent cover interspersed with open water, or with
peripheral bands of emergent cover encircling expanses of open water; and on intermittent
saline lakes

Sutter and Brigham 1998

Saskatchewan

Mixed-grass pasture, tame pasture

No significant difference in abundance was found between lightly grazed mixed-grass and lightly
grazed stands of crested wheatgrass (Agropyron cristatum)

Presence was positively associated with wetlands containing dense stands of emergent vegetation,
with open water or bare soil covering <5% of the wetland, and with adjacent uplands of alfalfa
(Medicago sativa)/hayland; presence was negatively associated with wetlands with adjacent tilled
fields; were observed on temporary, seasonal, and semipermanent wetlands, on intermittent streams,
stock ponds, dugouts, and tilled wetlands, but none were seen on permanent streams

* In an effort to standardize terminology among studies, various descriptors were used to denote
the management or type of habitat. "Idle" used as a modifier (e.g., idle tallgrass) denotes
undisturbed or unmanaged (e.g., not burned, mowed, or grazed) areas. "Idle" by itself denotes
unmanaged areas in which the plant species were not mentioned. Examples of "idle" habitats include
weedy or fallow areas (e.g., oldfields), fencerows, grassed waterways, terraces, ditches, and road
rights-of-way. "Tame" denotes introduced plant species (e.g., smooth brome [Bromus inermis]) that
are not native to North American prairies. "Hayland" refers to any habitat that was mowed, regardless
of whether the resulting cut vegetation was removed. "Burned" includes habitats that were burned
intentionally or accidentally or those burned by natural forces (e.g., lightning). In situations
where there are two or more descriptors (e.g., idle tame hayland), the first descriptor modifies the
following descriptors. For example, idle tame hayland is habitat that is usually mowed annually but
happened to be undisturbed during the year of the study.

Sutter, G. C., and R. M. Brigham. 1998. Avifaunal and habitat changes resulting from conversion of native prairie to crested wheat grass: patterns at songbird community and species levels. Canadian Journal of Zoology 76:869-875.